Field of the Invention
The present invention relates to roofing products exhibiting enhanced tear strength. More particularly, the present invention relates to non-woven glass fiber mats used to reinforce roofing products, with the products comprising a release agent, preferably a reactive polysiloxane.
Description of the Related Art
It is known to make reinforcing mats from glass fibers and to use these mats as substrates in the manufacture of a large number of roofing products such as shingles, built up roofing products, etc. Any known method of making nonwoven mats can be used, such as the conventional wet laid processes described in U.S. Pat. Nos. 4,112,174, 4,681,802 and 4,810,576, the disclosures of which are incorporated herein by reference. In these processes a slurry of glass fiber is made by adding glass fiber to a typical white water in a pulper to disperse the fiber in the white water forming a slurry having a fiber concentration of about 0.2-1.0 weight %, metering the slurry into a flow of white water and depositing this mixture on to a moving screen forming wire to dewater and form a wet nonwoven fibrous mat.
This wet nonwoven mat of glass fiber is then transferred to a second moving screen and run through a binder application saturating station where an aqueous binder mixture, such as an aqueous urea formaldehyde (UF) resin based binder mixture in water with about 24 weight percent, based on the dry weight of the UF resin, of a blend of 91.7 weight percent polyvinyl acetate homopolymer and 8.3 weight percent of an acrylic tripolymer, is applied to the mat. This is followed by sucking off the excess binder and drying the unbonded, wet mat and curing (polymerizing) the UF based resin binder which bonds the fibers together in the mat. Preferably, the aqueous binder solution is applied using a curtain coater or a dip and squeeze applicator, but other methods of application such as spraying will also work.
In the drying and curing oven the mat is subjected to temperatures of 250-450 or 500° F. for periods usually not exceeding 1-2 minutes and as little as a few seconds. Alternative forming methods include the use of well known processes of cylinder forming and “dry laying” using carding or random fiber distribution.
UF resins are most commonly used as a binder for fiber glass mats because of their suitability for the applications and their relatively low cost. Melamine formaldehyde resins are sometimes used for higher temperature applications. To improve the toughness of the mats, a combination of higher mat tear strength and mat flexibility, which is needed to permit higher processing speeds on roofing product manufacturing lines and for maximum roofing product performance on the roofs, it is common to modify or plasticize the UF resins with acrylic latexes or SBR latexes. Meeting the tear strength requirements for asphaltic roofing composites or shingles can also be achieved by increasing the weight of the mat and/or asphalt in the shingle. Such methods however, are very costly.
U.S. Pat. No. 6,993,876 discloses the use of an adhesion modifier treated glass fiber mat in a roofing composite. The adhesion modifier can be a non-reactive polysiloxane.
Hundreds of millions of pounds of glass fiber mat have been made by the above known processes and have worked well. It is nevertheless desirable to simplify the mat process, to reduce costs and to improve the tear strength of roofing products still further. The present invention provides these advances in the industry.